A medium voltage switching pole, comprising:
- a fixed contact of a vacuum interrupter;
- a movable contact of the vacuum interrupter;
- a piston;
- at least one electrical contact;
- a first terminal;
- and
- a second terminal,
- wherein the fixed contact is fixedly connected to the first terminal,
- wherein the movable contact is fixedly connected to the piston,
- wherein the piston is configured to move within the second terminal along an axis,
- wherein the at least one electrical contact is configured to make an electrical connection between the piston and the second terminal,
- wherein the at least one electrical contact is fixed to an inner surface of the second terminal,
- wherein an outer surface of the piston and an inner surface of the second terminal are configured such that:
- when in an open configuration the fixed contact and movable contact are separated from one another, at least one first radial line perpendicular to the axis extends through locations of the at least one electrical contact, and a first distance along the at least one first radial line extends from the outer surface of the piston to the inner surface of the second terminal, the outer surface of the piston having a first diameter along the at least one first radial line, and
- when in a closed configuration the fixed contact and movable contact are in contact with one another, at least one second radial line perpendicular to the axis extends through locations of the at least one electrical contact, and a second distance along the at least one second radial line extends from the outer surface of the piston to the inner surface of the second terminal, the outer surface of the piston having a second diameter along the at least one second radial line, the first distance being greater than the second distance, the second diameter being greater than the first diameter,
- wherein the at least one first radial line is at a same axial location as the at least one second radial line,
- wherein at one or more first longitudinal positions the outer surface of the piston has a circular cross section with a diameter of the first diameter,
- wherein at one or more second longitudinal positions the outer surface of the piston has a circular cross section with a diameter of the second diameter,
- wherein in a direction extending away from the movable contact a transition region joins the outer surface with the second diameter to the outer surface with the first diameter, and
- wherein when in transitioning from the closed configuration to the open configuration the piston is configured such that the transition region does not contact the at least one electrical contact.